House Speaker Robert A. DeLeo unveiled a proposal Tuesday for the most comprehensive changes to Massachusetts gun laws in 16 years, saying that the state cannot wait for federal action to curb gun violence.

Under the bill, local police would be given expanded discretion to consider a person’s “suitability” to own a gun, the state would join a national database for criminal and mental-health background checks, and all private sales of firearms would be conducted in the presence of a licensed dealer.

“I knew we had to do something,” said DeLeo, who listed, one by one, several fatal shootings that have occurred in the state since mid-May. “Our goal here in Massachusetts is to make serious and long-standing change.”

DeLeo said he hoped the bill, which was fueled in large part by the December 2012 shooting at the Sandy Hook Elementary School in Connecticut, could be enacted by the end of the legislative session in July. His press conference came days after a shooting and stabbing spree in California left six people dead.

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The proposal followed dozens of hearings and meetings held by lawmakers around the state, complemented by a separate study from a gun violence task force led by Jack McDevitt, associate dean of research at Northeastern University’s College of Social Sciences and Humanities.

McDevitt said many of the task force’s recommendations are reflected in the bill. “This legislation will reduce gun deaths in Massachusetts,” McDevitt said at a State House news conference to announce the bill.

Although Massachusetts has the nation’s second-lowest rate of gun-related deaths — a figure that includes accidents — homicides committed with firearms rose after the last comprehensive gun-control package passed in 1998.

In 2011, Massachusetts recorded 122 such homicides, a stark increase from 65 in 1998, according to data supplied by James Alan Fox, a Northeastern University criminologist. Nationwide, such homicides increased only 3 percent from 1999 to 2010, according to the federal Centers for Disease Control and Prevention.

From 1998 to 2011, firearm-related injuries in Massachusetts increased by 17 percent, according to the state Department of Public Health.

Gun-rights activists point to the trends as evidence that gun control does not work. Advocates for tighter gun laws, however, said that even more legislation and law-enforcement funding are needed.

The new proposal seeks to tighten and clarify state regulations about who can buy guns and how they can be bought. One potentially contentious change would give police the discretion to deny a permit for a rifle or shotgun if an applicant is deemed unsuitable.

Under current law, police can apply a vague standard of unsuitability for licenses to carry a gun. But police do not have that discretion in issuing the Firearms Identification Card, which allows Massachusetts residents who pass a background check to buy a small-capacity rifle or shotgun.

In an effort to establish uniform criteria across Massachusetts, the bill would require the state Executive Office of Public Safety to create specific standards for suitability.

Jim Wallace, executive director of the Gun Owners’ Action League, said the bill’s expansion of suitability criteria makes the bill unacceptable. “We were hoping for something we could support right off the bat, but it’s pretty clear we can’t,” Wallace said.

The proposal to conduct all private sales in the presence of a licensed dealer is problematic and redundant, said Wallace. Under current law, both buyer and seller must have gun permits that require a background check, Wallace said.

“It’s a problem that doesn’t exist that they’re trying to solve,” Wallace said.

DeLeo, however, said this provision is important to ensure that a gun can be traced at each step of a potentially years-long path from owner to owner. Somewhere along that chain of possession, DeLeo said, a gun can fall into criminal hands.

“Let’s get this straight: Lawful gun owners in this state aren’t the problem,” said Representative Harold Naughton Jr., a Democrat from Clinton who is House chair of the joint Committee on Public Safety Committee and Homeland Security, which toured the state to solicit ideas.

The bill would streamline the licensing process and also address a key concern of gun-rights groups — that legislation focus on keeping firearms away from the mentally ill — by requiring school districts to better meet the mental-health needs of students.

Schools would have to establish two-way communication with local police and fire officials. In addition, training of school staff to help prevent suicide, which lawmakers said accounts for 60 percent of gun deaths in the state, would be mandated.

Local authorities also would be mandated to trace any guns used in crimes, as opposed to current practices that can vary by community.

John Rosenthal, the cofounder of Stop Handgun Violence, which maintains a large billboard on the Massachusetts Turnpike that tracks gun-related deaths, said the proposal “makes Massachusetts safer without any undue inconveniences to gun owners.”

However, the House assistant minority leader, Representative George Peterson of Grafton, said the bill does not have enough teeth to reduce street violence and lacks money for important components.

“If we were able to fund some of the mental health issues in there, I think that would be a step in the right direction. If we were prosecuting quicker and more effectively, that would be a step in the right direction,” said Peterson, a Republican. “If there were something in here about straw sales and having a stiffer penalty for it, I’d support that.”

DeLeo said he is optimistic that the bill will attract support in the Senate and from Governor Deval Patrick.

In a brief statement, the state Executive Office of Public Safety and Security said the bill is “an important step forward in the advancement of public safety in the Commonwealth. We are, at present, carefully reviewing and analyzing the measure to determine its full effectiveness.”

Travis Andersen of the Globe Staff contributed to this report. Brian MacQuarrie can be reached at macquarrie@globe.com.